package com.coodroid.olympic.common;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/*
加密 – 
1.String encryptingCode = SimpleCrypto.encrypt(masterPassword,originalText);


解密 – 
1.String originalText = SimpleCrypto.decrypt(masterpassword, encryptingCode);
  
 */
   
public class AESString {    
   
    public static String encrypt(String cleartext,String seed) throws Exception {    
        byte[] rawKey = getRawKey(seed.getBytes());    
        byte[] result = encrypt(rawKey, cleartext.getBytes());    
        return toHex(result);    
    }    
        
    public static String decrypt(String encrypted,String seed) throws Exception {    
        byte[] rawKey = getRawKey(seed.getBytes());    
        byte[] enc = toByte(encrypted);    
        byte[] result = decrypt(rawKey, enc);    
        return new String(result);    
    }    
   
    private static byte[] getRawKey(byte[] seed) throws Exception {    
        KeyGenerator kgen = KeyGenerator.getInstance("AES");    
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");    
        sr.setSeed(seed);    
        kgen.init(128, sr); // 192 and 256 bits may not be available    
        SecretKey skey = kgen.generateKey();    
        byte[] raw = skey.getEncoded();    
        return raw;    
    }    
   
        
    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {    
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");    
        Cipher cipher = Cipher.getInstance("AES");    
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);    
        byte[] encrypted = cipher.doFinal(clear);    
        return encrypted;    
    }    
   
    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {    
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");    
        Cipher cipher = Cipher.getInstance("AES");    
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);    
        byte[] decrypted = cipher.doFinal(encrypted);    
        return decrypted;    
    }    
   
    public static String toHex(String txt) {    
        return toHex(txt.getBytes());    
    }    
    public static String fromHex(String hex) {    
        return new String(toByte(hex));    
    }    
        
    public static byte[] toByte(String hexString) {    
        int len = hexString.length()/2;    
        byte[] result = new byte[len];    
        for (int i = 0; i < len; i++)    
            result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();    
        return result;    
    }    
   
    public static String toHex(byte[] buf) {    
        if (buf == null)    
            return "";    
        StringBuffer result = new StringBuffer(2*buf.length);    
        for (int i = 0; i < buf.length; i++) {    
            appendHex(result, buf[i]);    
        }    
        return result.toString();    
    }    
    private final static String HEX = "0123456789ABCDEF";    
    private static void appendHex(StringBuffer sb, byte b) {    
        sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));    
    }    
        
}